Why do you consider this clickbait? It's not untrue, nor does it tease with hidden information alluded to in the title. It's a straight-forward headline describing the contents of the article.
It does tease with hidden information by making you want to read the article to see what "this disease" is. And the "unstoppable" bit, while true, reads as very sensationalist.
A less clickbaity title might be something like: "The Sudden Oak Death fungus has killed a million trees in California, and is no longer stoppable". Or something like that.. I'm no journalist.
The one on this link is fine, although if you want to be more newspaper-like I could you could say "Scientists: Sudden Oak Death Epidemic No Longer Stoppable"